CHAPTER 8 INTC
Preliminary User’s Manual A14874EJ3V0UM
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Figure 8-6. Servicing Example in Which Another Interrupt Request Is Issued During Interrupt Servicing (1/2)
Main routine
Servicing of <a>
Servicing of <b>
Interrupt request <b> is acknowledged because
the priority of <b> is higher than that of <a>
and interrupts are enabled.
EI
Interrupt request<a>
(level 3)
→
EI
Interrupt request<c>
(level 3)
→
Servicing of <c>
Servicing of <d>
Although the priority of interrupt request <d>
is higher than that of <c>, <d> is held
pending because interrupts are disabled.
Interrupt request<e>
(level 2)
→
Servicing of <e>
Servicing of <f>
Interrupt request <f> is held pending even if
interrupts are enabled because its priority
is lower than that of <e>.
EI
Interrupt request<g>
(level 1)
→
Servicing of <g>
Servicing of <h>
Interrupt request <h> is held pending even if
interrupts are enabled because its priority
is the same as that of <g>.
EI
Interrupt request<b>
(level 2)
→
Interrupt request<d>
(level 2)
→
Interrupt request<f>
(level 3)
→
Interrupt request<h>
(level 1)
→
Remarks 1.
<a> to <u> in the figure represent dummy names that are assigned to distinguish between the
interrupt requests.
2.
Higher or lower default priorities mentioned in the figure indicate relative priorities between two
interrupt requests.
Caution To use multiple interrupt servicing, the contents of the EIPC and EIPSW registers must be
saved.